The effects of colchicine and vincristine on the concentrations of glucose and related metabolites in goat's milk.

The effects of colchicine and vincristine on the concentration of glucose and its metabolites in milk were studied following intramammary injection of the alkaloids into one mammary gland of lactating goats. Both alkaloids decreased the rate of milk secretion from the treated gland and produced similar changes in the concentrations of various metabolites in milk. The concentrations of glucose, UDP-galactose, galactose, pyruvate and lactate increased, while those of glucose 6-phosphate and phosphoenolpyruvate decreased in milk from treated glands. The rate of milk secretion from the untreated gland increased, along with the concentrations of glucose in the milk. The changes in the concentrations of the metabolites in milk are discussed in relation to possible biochemical changes occurring in the mammary gland during the suppression of milk secretion by the alkaloids. It is suggested that, before alkaloid treatment, the rate of milk secretion was limited by intracellular glucose supply.